The invention relates to distributing apparatus and a method for communication using the same. More particularly, it relates to distributing apparatus and the like for transmitting a signal to or receiving a signal from transmitting-and-receiving modules of wireless terminals connected with a wiring scheme when performing an assessment and/or development of a wireless terminal or software therefor.
In a case where a wireless terminal or software for it should be assessed and/or developed, wireless terminals can be connected to each other with a wiring scheme such as using co-axial cable in order to achieve steady communication between them to keep away from being affected by any noise from outside or a reflected wave.
Distributing apparatus that divides a signal into two parts has been widely known (see pages 2 and 3 of Japanese Patent Application Publication No. 2000-307313 and FIG. 1 thereof).
In this case, such distributing apparatus has an input terminal, two distribution terminals, two branch lines each having a line length of a quarter of a set wavelength or a quarter of a set wavelength adding integral multiple of a half of the set wavelength, each of which is connected to the input terminal and the distribution terminal, and isolation resistor that is connected to the distribution terminals.
Alternatively, proposed has been a distributing apparatus that distributes a signal received at an input port thereof to plural output ports (see pages 3 and 4 of Japanese Patent Application Publication No. H09-246817 and FIG. 1 thereof).
In this case, such the distributing apparatus distributes high-frequency power to plural ports or synthesizes the power. It is composed of transmission lines that are laminated on dielectric substrate, such as slot circuit, which is formed with dielectric multilayer thin films and metal thin films, balanced lines made of parallel plates, coplanar lines, strip lines, and micro-strip lines. It has a serial distribution-in-two circuit, which is formed so that a first transmission line that is composed of slot lines or balanced lines made of parallel plates, having characteristic impedance of Z can be connected with second and third transmission lines each of which is composed of slot lines or balanced lines made of parallel plates, having characteristic impedance of Z/2. It also has a parallel distribution-in-two circuit, which is formed so that a fourth transmission line that is composed of coplanar lines, strip lines, or micro-strip lines, having characteristic impedance of Z′ can be connected with fifth and sixth transmission lines each of which is composed of coplanar lines, strip lines, or micro-strip lines, having characteristic impedance of 2Z′. It further has line conversion parts, each of which connects the second or the third transmission line to the fourth transmission line that are connected between the serial distribution-in-two circuit and two parallel distribution-in-two circuits. Thus, in the distributing apparatus, one serial distribution circuit is connected to two parallel distribution circuits so that if characteristic impedance of the first transmission line is set to Z0, characteristic impedance of each of the fifth and sixth transmission lines can equal to Z0.
Additionally, proposed has been a microwave-power-distributing apparatus (see pages 3 and 4 of Japanese Patent Application Publication No. H08-293707).
This microwave-power-distributing apparatus achieves reduction in transmission loss with a waveguide configuration of its power distribution part.
As described above, in a case where a wireless terminal or software for it should be assessed and/or developed, it is necessary that the wireless terminal can receive only an electric wave from another wireless terminal without any influence of noise from the outside in order to achieve steady communication between the wireless terminals and avoid being affected by any noise from the outside or a reflected wave. It is also desirable to connect the wireless terminals to each other with a wiring scheme in order to prevent the wireless terminals from being affected by any interference between a direct wave and a reflected wave.
In the past high-frequency-power-distributing apparatus such as a Wilkinson coupler, a hybrid coupler, or their combination, however, it has been difficult to implement an assessment and development system which can make the insertion loss between the ports constant. If any past distributing apparatus and an attenuator are combined to implement an assessment and development system, which is available, not ideal, such system may have a large configuration.
For example, in a case of the above distributing apparatus disclosed in Japanese Patent Application Publication No. 2000-307313, it is difficult to implement an assessment system for wireless terminals which can distribute a signal evenly to every port. In this case, it is necessary to use a combination of the attenuator and the distributing apparatus in order to set the strength of the signal thereof to a desired value. This causes a large and complicated network system to be constructed.
Further, in a case of the above distributing apparatus disclosed in Japanese Patent Application Publication No. H09-246817, the input and output ports are specified and the insertion loss between all the ports fails to be fixed, thereby making at least three wireless terminals unavailable for assessment.
In a case where the above distributing apparatus of low loss disclosed in Japanese Patent Application Publication H08-293707 is used for assessing the wireless terminal, a receiving side may receive a distorted signal because the signal is too strong. In order to mitigate it to implement steady wireless communication, it is necessary to send to the receiving side a signal that has been attenuated by a certain level.
It is desirable to present a distributing apparatus and a method for communication using the same which can fix the insertion loss between the ports in which wireless terminals can communicate to each other under similar conditions, and by which the distributing apparatus can be made inexpensive and downsized.